The present invention relates to an endoscope comprising an inserting portion insertable into, for example, a body cavity of a subject, an interior of a machine, or the like, to perform observation and, more particularly, to an operating mechanism for a resiliently bendable section of the inserting portion.
A usual, conventional endoscope comprises an operating body and an inserting portion extending therefrom. The inserting portion has a distal end section formed into a resiliently bendable section. An angularly movable member such as pulley or the like is mounted, within the operating body, on a shaft for angular movement therewith around an axis thereof. An operating member such as lever is connected to an end of the shaft which projects outwardly from the operating body. The angularly movable member is operatively connected to a distal end of the bendable section through a pair of operating wire sections.
An operator or operating surgeon inserts the inserting portion of the endoscope into, for example, a body cavity of a subject and, thereafter, he turns the operating lever to angularly move the angularly movable member around the axis of the shaft. The angular movement of the angularly movable member is transmitted to the bendable section through the operating wire sections to bend the bendable section toward any desired direction.
As the bending angle of the bendable section increases, the restoring force of the bendable section tending to return to its original straight condition increases. However, since the operating surgeon turns the operating member with his hand gripping the operating body, he cannot apply his so great turning force to the operating member. Consequently, it is difficult for the operating surgeon to greatly bend the bendable section against the restoring force thereof.
As disclosed in Japanese Patent Publication No. 56-13455 and Japanese Utility Model Application Laid-Open No. 58-160002, an arrangement has been proposed in which an electric motor is used as a power source and is directly connected to the shaft of the angularly movable member. With such arrangement, however, it is required for the motor to be rotated at low speed and to output high torque. Thus, the endoscope is increased in overall dimension and is also increased in weight, so that the operability of the endoscope is reduced.
In order to eliminate the above disadvantage, a construction has been proposed in which a small electric motor is used in combination with a gear train having high reduction ratio, to obtain high torque within a low rotational speed range of the motor.
With the construction described above, in the event that the failure of electric power supply, malfunction or the like occurs and it becomes necessary to manually operate the endoscope, force must be transmitted in the direction opposite the usual direction, that is, the operating surgeon has to operate the operating member to angularly move the angularly movable member, to thereby rotate the motor. However, since the gear train is used which has a high reduction ratio, the power transmitting ratio of the gear train is low. In addition, magnetic force acts between rotor and stator of the motor. Accordingly, it is not easy for the operating surgeon to rotate the motor. This renders it considerably difficult for the operating surgeon to manually operate the endoscope.
In particular, in the event that the failure of electric power supply occurs after the inserting portion has been inserted into the body cavity of the subject and the bendable section has been bent to a desired angle, it might be no longer possible to withdraw the inserting portion out of the cavity of the subject, because it is impossible to release the bent condition of the bendable section.